---------------------- multipart/alternative attachment Bob D writes and Del responds: > >> >> 1) Is there some small change to try next, to improve the treble sustain >> and projection, without changing the rib layout, or making a new bridge >> root? >> > You might try a soundboard cutoff bar.[SNIP] You might start by recapping > the top two treble sections to accommodate something resembling semi-log > scaling. I think I can handle a cutoff bar. Is it necessary to have something showing on the top side of the board, or can it all be underneath? Ron N mentioned that you posted a picture of an A showing cutoff bar, and I can't find it in my files. Can you send it to me? He also mentioed belly rail and long side stiffeners, which I can also live with. And can you point me to the math for semi-log scaling? > > > >> 2) I thought the general deal was that stiffer=softer tone/longer sustain >> and less stiff=louder, more abrupt. We recently strung a Chickering 109C, >> the treble of which had both weak output AND a very short sustain in the >> top section. The scale lengths and sizes looked normal. Whassup? Too much >> mass? >> > What do you mean, "The scale lengths and sizes looked normal....?" What is > normal? Where is the hammer striking point? What are the hammers like? By "normal" I meant they were very similar in the treble to a Steinway A which sounded very much better. It had some crown, not lots, and we put bearing on it commensurate with the crown. The hammers shouldn't matter, since the weakness was also obvious when the strings were plucked. All but the high treble sounded good. I wasn't sure where to look next. > > > >> 3) A third bridge obviously goes on a different spot on the soundboard, >> with different impedance, and loudness, characteristics from the >> hockey-stick area of the tenor bridge it replaces. How does one figure >> that difference into the string scale the FIRST time? And would you leave >> the hockey stick area or cut it away? >> > Are you going to be in Dallas come July? > Alas, it isn't looking like it. I saw your day-long class in Chicago, and have been perusing the PTJ disks. Eagerly awaiting your book..... > > >> 4) What difference do you think the grain angle to the belly rail makes? >> > In general, as the grain angle becomes closer to perpendicular to the > bellyrail the stiffness felt by the bridge increases [SNIP SNIP] Around the > bass bridge this added stiffness may not be desirable since it will work to > increase the sustain of the higher partials, something rarely desirable in > the bass section. Compensation can be made by thinning the board out > through the bass region or, better yet, partially or fully floating the > bass region. > > It is a good idea to re-orient the ribs to take advantage of any changes > made to the soundboard grain angle. Though we don't always. Thanks, I understand the concept now, except for how to re-orient the ribs. Do you mean swing them around in the tenor/bass to keep them perpendicular to the grain of the sbd in the bass to help keep the stiffness down, or what? Could they be thinned slightly instead? Sounds like we will save this for another board, because of the multiple changes, and because I don't think this customer would be happy with a slot in his board. Maybe the M&H A which follows it. I think Dale Erwin floated a M&H A board with success. I'll see if I can get a look at it. Thanks, Bob Davis ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/f6/58/38/89/attachment.htm ---------------------- multipart/alternative attachment--
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